In NW Moroccan traditional medicine, the seed oil is applied in the treatment of cutaneous infections (Merzouki et al. 2000).

The seeds (linseed) yield an oil by pressure and the remaining "cake" is used for cattle-feed. Dermatitis and ulceration on the dorsa of the feet in gatherers of flax was attributed to contact with wild chamomile ("manzanilla silvestre" — possibly Anthemis cotula, fam. Compositae) growing in the fields (D'Agostino 1927, 1935). Positive patch tests to the leaf of Linum were observed by Szego (1965). The sharp points of the seeds can cause mechanical injury. Insect parasites can cause pseudophytodermatitis in flax gatherers. Irritant oils of mustard and rape (Cruciferae) can contaminate the flax (Barnes 1931). Flax seed hair tonic caused contact dermatitis (Ramirez and Eller 1930). Burlap sugar bags (of jute, fam. Tiliaceae) in which the linseed is shipped, irritated longshoremen (Schwartz et al. 1957). Linseed oil produced a positive patch test in one of 45 painters investigated for contact dermatitis; three-quarters of them were contact sensitive to turpentine (Pirila 1947). Acneform folliculitis in flax-spinning mills resulted from oils (sperm oil, etc.) used on the machinery (Purdon 1874, Purdon 1902, Prosser White 1934).

Linimentum Calcis, otherwise known as Linimentum Calcis cum Oleo Lini, and also as Liniment of Lime, Liniment of Lime with Linseed Oil, and as Carron Oil, is a liniment prepared by mixing and agitating together equal parts of lime water and linseed oil. Pereira (1842) noted that it "has long been celebrated as an application to burns and scalds, and is employed for this purpose at the Carron Ironworks — hence one of its names." [The Carron Company was an ironworks established in 1759 on the banks of the River Carron near Falkirk, in Stirlingshire, Scotland]. This liniment was formerly officinal in the US Pharmacopoeia, the British Pharmaceutical Codex, and in the pharmacopoeias of France (as "Liniment Calcaire"), Germany (as "Kalkliniment"), Italy (as "Linimento de Calce") and Spain (as "Linimento Oleo-Calcareo"). Alternative formulations substitute linseed oil with olive oil; turpentine oil and pennyroyal oil have also been included in the formulation (Felter & Lloyd 1898).

Workers with flax in the moist state developed allergic contact dermatitis of the exposed parts. Flax-spinners can develop exfoliation of the skin of the hands and finally ulceration. Flax-soakers can develop vesicular dermatitis of the hands probably from the hot chemical solutions employed (Leloir 1885, Leloir 1892, Downing et al. 1932, Prosser White 1934).

An intradermal test with linseed cake produced urticaria (Rajka 1948). Linseed cake can produce dermatitis in extractors of linseed oil; the dermatitis occurs on the extensor surfaces of the hands and forearms, occasionally on the upper arms and face and on the legs (Vokoun 1927). Seeds, used for pressing, from South America and India, were found to be more liable to cause dermatitis than seeds from Canada and the United States.

Flax seed in a mixed breakfast cereal (also containing wheat and rye) cooked as a porridge caused tingling and burning of the lips and tongue. Skin testing with the cereals produced wheals after 15-30 minutes only with the flax seed. Neither linen nor linseed oil produced a reaction. The only previous contact the patient had had with flaxseed was about 20 years earlier when a flaxseed poultice was applied to a carbuncle on the leg for a period of about 10 days. A second very similar case was also reported, again with a history of previous exposure to a flaxseed poultice (Black 1930).

The incidence of linseed dermatitis varies with the source of the seed and the season of the year; the oil may produce a follicular eruption (Barnes 1931). Linen spinners can develop traumatic lesions of the hands and hyperkeratosis of the palms, paronychia and vasomotor disturbances of the hands together with irritation from the chemicals used in hot solutions for washing the fibres (Meneghini and Gianotti 1953). Flax in cigarette paper produced dermatitis; the flax fibre, cooked and bleached, prior to the paper-making process, also produced positive patch test reactions (Tye 1950). Linseed oil may be irritant and occasionally sensitising (Schwartz et al. 1957). Pure linseed oil was found to be non-irritant by patch test (Greenberg and Lester 1954). Linseed oil can be contaminated with rape seed oil (Brassica napus fam. Cruciferae). Flax-workers are subject to irritant dermatitis from paraffin and coarse raw hemp can irritate the skin (Kinnear et al. 1955). Subcutaneous nodules followed a sixth injection of mercury salicylate in linseed oil (Sutton 1923). Flaxseed applied as a poultice caused urticaria (Derbes and Coleman 1972). Type I hypersensitivity to flax was demonstrated by Nicholson (1927).

Prosser White EW, in discussion of Nixon (1944), referred to reported outbreaks of "linseed itch" as well as "cheese itch" and "copra itch" in dock labourers, implying that the condition was a pseudophytodermatitis caused by mites. Occupational contact sensitivity to flax seed and to linseed oil was reported in a seaman exposed to flax products; he was also contact sensitive to Ambrosia (ragweed) and other Compositae species (Jordan et al. 1942).

Oil of Linseed, considered to be a known allergen, is removed from certain brand-name cosmetics (Anon 1973).